Sweat Rate and Sodium Intake Questions

Just like with calories, there's no way to replace 100% of the fluid and salt that you lose while training and racing. Someone once gave me a rough guestimate to do (Weight * 4) g of electrolytes per hour. I'm in the 150s and do 650g electrolytes on the bike and around 600 on the run. It's easy on the bike; I customized an Infinit mix to give me what I need. On the run I do 2 Powergels (200g salt) + 2 salt pills.

There's no way to replace all the water you lose to sweat. I just drink as much as I can without getting the sloshy stomach effect. Usually I do 20oz per hour on long runs when it gets warm (70+).

I think there is a rule on dehydration that says 5% or so weight loss is the max you want to allow for. After that you start getting woozy and such. Could be wrong on that number though.

I am right there with you in the heavy sweating dept.  At one point last summer I did a 1:20 run and dropped in the neighborhood of 9lbs of water weight.  That put me right around 100oz per hour.  Obviously I can't drink 6+lbs of water an hour.  I think the more important thing is to replace the electrolytes that you burn and try to get as much water as you can that can be absored.  Even if you can get the amount of water into your stomach you will probably pee alot of it out and it will do no good anyways.  I have been told that you can train you body to absorb more water though.  Not exactly sure but you might be able to seach the web.  As far as salt intake goes, I just started using the s-caps and they work great.  I did my first century ride last weekend and had no cramps until mile 97 and then only 1 small one using 2-caps.  A few weeks earlier I did 80 miles on complete flat ground (alot of wind though) and started to cramp at mile 70 pretty severly with no s-caps.  Not sure if it is all the 2-caps but I am going to keep using them.

Compared to most electrolyte pills you only need 1 maybe 2 per hour not 5 or 6.

That is not quite correct ... the calculator tells you that you LOSE about 66 oz. per hour.  That is not how much you necassarily can take in.  That depends on your absorption ability and other intangibles.

My sweat rate has been almost that high in some tests and on the bike I have adapted to taking two 24 oz. bottles an hour.  On a run I just cannot do that.

Trial and error

I am 230# and a heavy sweater.  I use Infinit and normally take in 500 mg per hour of sodium.  I am adding 350 or so with S caps for IMAZ

I stand corrected.  It's 66oz/hr sweat rate.  I guess I just figure you should take in what you expend over a long period/race to avoid dehydration.  Maybe I need to reexamine that theory.

Thanks

It is physically impossible to replace in the period that you are working out what you sweat and what you expend in glycogen.

By eating/drinking during a longer workout/race you are basically just trying to staunch the rapid bleeding of your energy.

ChrisM - 2008-03-31 2:28 PM Although I do know a guy that gained weight at IM Switz and qualified

It's not impossible, but it's more dangerous than dehydration.

I have read that for each 16 oz of sweat it is 400-600 mg of sodium lost but various by person.

I have in the past paid attention to sodium intake in summer but not so much in the winter. Lately on long rides I've had some issues at end of rides and after so I've been tracking my sodium now even when it is 30 and since I've been taking in more I'm feeling better. One key I use if I sweat and have crust on me afterwards I need more sodium.

The tough issue is that you can take in to much sodium and have issues. What I did in the summer was start at a level and see how that worked, then upped that amount slowly. It would be cool to be able to go to the Gatorade Institute in CO (I think that is what is is called) where they do actually testing but not possible for us normal folks.

You can train yourself to drink more. I now drink 46 oz/hour running but back a year ago I drank about half that amount.

I just keep a spreadsheet with various sweat tests and weather conditions. The other thing that occurs the fitter you become the more you will sweat. My sweat rate went from 20 oz/hour, to 33 oz/hour, to 56 oz/hour on the run from 2005 to 2007. So you need to keep checking it.

Great job on working on this now...important to racing and training well.

Thanks, that's good to know.  I was really starting to think I was going crazy.  I have noticed that I have been sweating more (or at least I thought I was) but guessed it could just be in my head.  This would seem to confim my sanity....